WO 2005/124063 describes a shelter that includes a ground sheet and a cover; the space between the ground sheet and the cover can be inflated by pumping air into the space to raise the cover and form the shelter. The cover is made of a fabric that has been impregnated with cement; the fabric may be a type of felt known as “wadding”, which is a loose non-woven fabric. Immediately before the interior space is inflated, the cover is wetted with water, so that, after inflation, the cement in the cover sets and forms a rigid shell that acts as a self-supporting roof for the shelter, which is particularly useful in providing temporary accommodation in emergency areas.
WO2007/144559 discloses a fabric comprising a pair of opposed faces and self-supporting yarns (also called linking fibres) extending between the faces that maintain the faces in a spaced-apart arrangement and a solid powder material located in the space between the faces. The powder material is capable of setting to a rigid or semi-rigid solid mass on the addition of a liquid or on exposure to UV radiation and may comprise cement that will set to solid cement or concrete on the addition of a water-based liquid. The amount of settable material in the space in the fabric is such that, particularly when the material has set, it occupies substantially the whole of the space between the first and second faces. The fabric (without the powder material) may be spacer fabric, which is known and commercially available. The thickness of the spacer fabric is determined during manufacture by choosing an appropriate length for the linking fibres.
U.S. Pat. No. 4,495,235 discloses a flat body containing a core made of cement and aggregates placed between a cover layer and a backing layer. The layers and the cores are needle bonded together prior to the hardening of the cement so that the layers will hold together in a deformable state.
The term “cloth” or “filled cloth” will be used in the present specification to denote a spacer fabric having an internal space containing settable powder material. A “spacer fabric” is a fabric having a first face and a second face separated from each other by a space and also has self-supporting linking fibres extending between the first and second faces that maintain the first and second face in a spaced-apart arrangement. The settable powder material will also be referred to as the “fill”; the fill may include both material that reacts with the liquid to cause the fill to set, which will be referred to as the “reagent”, and materials that do not react with the liquid, e.g. auxiliaries and inert materials such as fillers.
One problem with powder filled cloth is that the fill spills out of the open edges of the spacer fabric, causing a mess during the manufacture, transport and use of the cloth, and the loss of the fill in the edge region of the fabric makes the properties of the edge region different from those of the rest of the cloth, and often the edge region must be removed when the cloth is used. Additionally some powdered fillers, particularly those having a melting temperature that is substantially different from the fibres of the spacer fabric, for example cement and most fillers, make heat cutting and sealing difficult or impossible for two reasons: firstly, they remain as powders and clog the melted plastic preventing it acting as a sealing material and secondly they increase the heat input required for effective heat cutting and clog the cutting blade preventing it from melting the spacer fabric fibres neatly. Therefore in order for heat sealing to work the cloth must be cut mechanically and the powder must be first removed from the edge being sealed; a preferred method is to suck the powder out in the area adjacent to the edge using a vacuum, then apply heat and pressure to seal the faces. However the multiple steps in the process make it time consuming and laborious or require expensive and bulky machinery, also the process is often unreliable and slow due to the requirement to have a dust free surface for effective heat sealing.
A further problem with filled cloth is that it is difficult to control the amount of liquid that is added during the setting procedure. If the amount of liquid added is less than that required to completely set all the reactive material in the fill, some of the reactive reagent will be wasted and could have been replaced by cheaper inert filler. Ultimately, a region may remain in the middle of the cloth that contains unset material, resulting in a significant reduction in the properties of the cloth. Although a problem initially, if the setting liquid is water and the cloth comes into contact with water in use, e.g. because it is exposed to rain, then the reagent may become fully set in use. More generally, particularly where the amount of liquid added is only slightly less than the optimum the unset material will be distributed throughout the set material resulting in only slightly lower than optimum mechanical properties.
On the other hand, if too much liquid is added, the consequences can be much more severe, for example the fill may be converted into a slurry and washed out of the cloth. Also, the excess liquid will not react and instead will remain within the fill while the reagent sets; the liquid may drain out of the cloth after setting, leaving voids in the set fill, thereby reducing the density of the set material. This can result in a high level of porosity in the final set product, which can result in a significantly lower final strength and also a lower resistance to liquid ingress, which is undesirable for applications where the cloth acts as a barrier to liquids. Furthermore a high level of porosity can result in other undesirable properties, for example: an increase in susceptibility to freeze/thaw damage and chemical attack.
The adding of the correct amount of liquid is time-consuming and requires the use of trained personnel.
The present invention provides improvements in filled cloth and especially provides a solution to the above problems.